feat(Gateway API): improve annotations support

[Dadeos-Menlo]

Description

The generation of DNS records from Gateway API resources involves combining information from a …Route resource and a Gateway resource. The current implementation, for the most part, only considers annotations from the Route resource. There are potential scenarios whereby it may be more convenient to assign annotations to the Gateway resource, thus ensuring that all DNS records associated with the given Gateway are similarly effected. An extreme example of such a scenario being when no Hostname information is specified (i.e. the given Gateway should accept any communication, irrespective of the DNS name used to establish it) but that a DNS record is desired to cover all Routes associated with the Gateway; in which case it would be convenient to apply an external-dns.alpha.kubernetes.io/hostname annotation to the Gateway itself, rather than having to apply annotations to every associated Route and having to deal with the potential confusion arising from precisely which Route owns the shared DNS record.

The proposed changes include:

• Adding validation of resource endpoint label ownership to all of the Gateway related unit-tests
• Refactor the process of Endpoint generation in order to preserve the relationship between Route and Gateway resources
• Consider annotations from both Route and Gateway resources when generating an Endpoint
  • In cases where the same annotation is present on both Route and Gateway resources, the Route derived value is used in preference
  • external-dns.alpha.kubernetes.io/ttl annotations are merged to yield the lowest specified value
  • In the case where external-dns.alpha.kubernetes.io/hostname is specified on a Gateway and that Gateway is the only Gateway contributing to an Endpoint the resource label is recorded as referring to the Gateway rather than the Route

No changes to the documentation are proposed because it currently implies that annotations on Gateway resources are supported, whereas in reality such annotations are only honoured when specified on Route resources.

Checklist

• Unit tests updated
• End user documentation updated

[k8s-ci-robot]

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @Dadeos-Menlo. Thanks for your PR.

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[mloiseleur]

/ok-to-test
Would you please add documentation on this feature ?

[mloiseleur]

@abursavich do you think you can do a first review on this PR ?

[Dadeos-Menlo]

Would you please add documentation on this feature ?

What additional documentation do you feel would add clarity?

In my opinion the proposed changes merely bring the implementation in line with the existing documentation.

No changes to the documentation are proposed because it currently implies that annotations on Gateway resources are supported, whereas in reality such annotations are only honoured when specified on Route resources.

[mloiseleur]

What additional documentation do you feel would add clarity?

In current documentation, the behavior when there are annotations on both Gateway & HTTPRoute is not detailed: no explanation and no example.

[mloiseleur]

/retitle feat(Gateway API): improve annotations support

[ivankatliarchuk]

Hi @Dadeos-Menlo . Nice work. Would it be possible to extract the refactoring into a separate pull-request to simplify a review and reduce blast radius?

Refactor the process of Endpoint generation in order to preserve the relationship between Route and Gateway resources

You could add tests as well that highlights current/incorrect behaviour to it.

[Dadeos-Menlo]

Hi Ivan,

In the interests of easing any review I separated the proposed changes into stand-alone commits. The sequence of which were broadly described by the bullet points provided in the initial description. My intention with these stand-alone commits was to mutate the pre-existing implementation, step-by-step, into one that exhibits what I consider to be more desirable behaviour (i.e. the consistent honouring of annotations assigned to Gateway resources).

The initial commit seeks to introduce additional unit-tests/expectations, regarding the Labels associated with every Endpoint generated from the various …Route/Gateway combinations exercised by the pre-existing tests. This commit avoids making any changes to the existing implementation, thus demonstrating that the asserted behaviour is representative of the current/existing behaviour.

The second commit seeks to refactor the existing implementation into a form conducive to tracking the relationship between …Route and Gateway resources throughout the processing required to generate the Endpoint objects. This commit avoids making any changes to the unit-tests, thus demonstrating that the asserted behaviour of the proposed, refactored, implementation is equivalent to that provided by the original implementation.

The third commit builds upon the refactored implementation in order to provide the intended additional functionality; namely the consistent honouring of annotations assigned to Gateway resources. This commit introduces new unit-test scenarios, associated with annotations being assigned to Gateway resources and in support of the proposed new behaviours, whilst avoiding modification of existing unit-test scenarios, thus demonstrating no regressions with respect to pre-existing asserted behaviours (NB: The essence of the "DualStack" tests were incorporated into the Gateway annotation orientated unit-test scenarios introduced).

The forth, and final, commit modifies the documentation as requested.

In direct response to your questions:

Would it be possible to extract the refactoring into a separate pull-request to simplify a review and reduce blast radius?

Whilst this would be possible, I consider that the proposed changes belong together in a single pull-request, and have made efforts to separate the mutations applied as outlined above.

You could add tests as well that highlights current/incorrect behaviour to it.

I consider that unit-test scenarios asserting the intended behaviour of annotations assigned to Gateway resources have been introduced, as part of the behavioural modifications proposed in commit three.

I hope that the explanation offered above aids your understanding and consideration. Thank you for your interest in these proposed changes.

Regards,

Peter